The objectives of this proposal are: (1) to study the effect of dietary lipids on the metabolic activation of chemical carcinogens and (2) to correlate the enzyme activities of the liver and mammary gland with the neoplastic development. Tallow, corn oil and coconut oil will be used as the dietary lipids and N-2-fluorenylacentamide (FAA), the chemical carcinogen. Male and female weanling rats will be fed ad libitum for 6 months an otherwise adequate but lipid-free diet supplemented with the above lipids at the 2 or 20 level. From the 2nd to the 5th month, 20 animals in each dietary group will receive the experimental diet supplemented with FAA at the 0.005-0.03% level while the remaining 10 animals will continue to receive the FAA-free diet. Both the experimental and control groups will receive the FAA-free diets during the 6th month. At the end of the experiment, the carcinogenesis in the liver and mammary gland will be studied. The enzyme activity of the S-9 and S-150 fractions of the liver and mammary gland will be determined by the in vitro production of ultimate mutagen(s) with a bacterial tester system or by other physical-chemical procedures.